Harlow, Olivia S.

Abstract The intestinal epithelial barrier is vital in preventing translocating bacteria and subsequent systemic infections. This protection is provided by host factors, by the intestinal microbiota, and, during early life, by breast milk. While the beneficial functions of breast milk are numerous to the nursing infant, it has been observed that proteins such as antibodies and growth factors are secreted in higher concentrations early during lactation and decrease as the milk matures. One such growth factor, epidermal growth factor (EGF), regulates the development of colonic goblet cell-associated antigen passages (GAPs). Decrease of EGF through disruption of synchronous breastfeeding or deletion of the epidermal growth factor receptor from goblet cells alters the kinetics of GAP formation, which can serve as a passage for pathogenic bacteria. In a murine model of early GAP formation utilizing an inhibitor of EGF receptor, we observed a variety of gut-resident pathogens were able to utilize GAPs to disseminate systemically and cause disease, including Escherichia coli, Enterococcus faecalis, Enterobacter cloacae, and Pseudomonas aeruginosa. In human studies, we found a strong correlation between concentrations of EGF in the diet and stool of very low birth weight infants. Notably, formula-fed infants contained significantly less EGF in both diet and stool. Future work will assess EGF in donor milk, which we find has highly variable EGF concentration. This work has strong implications for how diet influences risk of developing infections from gut-resident pathogens and how maternal EGF present in breastmilk is synchronized to the newborn infant to provide appropriate protection in early life. Supported by grants from NIH (AI144721, DK122187)

Abstract Neonatal sepsis remains a leading cause of death in preterm and low-birthweight infants and can be separated into two groups: early-onset sepsis (EOS) and late-onset sepsis (LOS). Previous studies have shown that LOS can result from translocation of enteric bacteria across the intestinal epithelium, resulting in bloodstream infection. Through metagenomic sequencing we have observed, unsurprisingly, potential sepsis-causing organisms such as Escherichia coli, Staphylococcus aureus, Enterobacter cloacae, and Group B Streptococcus (GBS) in the stool of neonatal intensive care unit patients. Our previous work has shown E. coli can disseminate from the intestines via goblet cells in a model of LOS, but how other bacterial pathogens disseminate remains unclear. GBS is often associated with EOS following in utero infections and vertical transmission from the mother during pregnancy and delivery. However, the ability of gut-residing GBS to cause sepsis in a murine model of LOS is still unknown. Here we infected five-day-old mice by oral gavage with different strains of GBS, but we did not observe GBS translocating the intestinal epithelium in the pups, unlike E. coli. We next induced EOS in newborn mice by vaginally inoculating pregnant mice to assess GBS dissemination and compare the EOS model to our LOS model. After in utero infection, most pups were intestinally colonized with GBS and, interestingly, only pups with GBS colonies in the lungs had systemic GBS infections. This data suggests neonates are at risk of GBS infection in utero, but not following delivery, even if GBS colonizes the neonatal intestine. This work could elucidate the pathogenesis of EOS as compared to LOS, leading to a deeper understanding of modes of GBS transmission. Supported by NIH: DK122187